Runtime obj loader texture error

Hi everyone,
I have a 3D model (obj.) wich I upload to runtime with the Runtime Obj Importer asset.
The problem is that if i apply a texture with some transparent parts, to a material, these parts become white.
Can you help me?

Shader:

Code (CSharp):

1. Shader "Custom/CullOffShader" {
2.     Properties {
3.         _Color ("Color", Color) = (1,1,1,1)
4.         _MainTex ("Albedo (RGB)", 2D) = "white" {}
5.         _Glossiness ("Smoothness", Range(0,1)) = 0.5
6.         _Metallic ("Metallic", Range(0,1)) = 0.0
7.         //Properties
8.         _EmissionLM("Emission (Lightmapper)", Float) = 0
9.         [Toggle] _DynamicEmissionLM("Dynamic Emission (Lightmapper)", Int) = 0
10.     }
11.     SubShader {
12.         Tags { "RenderType"="Opaque" }
13.         LOD 200
14.         Cull Off
15.  
16.         CGPROGRAM
17.         // Physically based Standard lighting model, and enable shadows on all light types
18.         #pragma surface surf Standard fullforwardshadows
19.  
20.         // Use shader model 3.0 target, to get nicer looking lighting
21.         #pragma target 3.0
22.  
23.         sampler2D _MainTex;
24.  
25.         struct Input {
26.             float2 uv_MainTex;
27.         };
28.  
29.         half _Glossiness;
30.         half _Metallic;
31.         fixed4 _Color;
32.  
33.         // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
34.         // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
35.         // #pragma instancing_options assumeuniformscaling
36.         UNITY_INSTANCING_BUFFER_START(Props)
37.             // put more per-instance properties here
38.         UNITY_INSTANCING_BUFFER_END(Props)
39.  
40.         void surf (Input IN, inout SurfaceOutputStandard o) {
41.             // Albedo comes from a texture tinted by color
42.             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
43.             o.Albedo = c.rgb;
44.             // Metallic and smoothness come from slider variables
45.             o.Metallic = _Metallic;
46.             o.Smoothness = _Glossiness;
47.             o.Alpha = c.a;
48.         }
49.         ENDCG
50.     }
51.     FallBack "Diffuse"
52. }

3D model with transparent texture


Material preview

Applied texture



Thank you